Ch. 20 LC

Researchers are using aerial photography (i.e., remote sensing) to estimate the productivity of a large stretch of Midwestern prairie. By quantifying the percent of the total land that contains live vegetation at different times over the growing season, the researchers hope to determine the average productivity of the prairie during the year. In the first picture taken on 1 April (day 1), the researchers estimate that 4 percent of the land is covered by living vegetation. On day 50, the vegetation cover is 29 percent. On day 100, the vegetation cover is 48 percent. On day 150, the vegetation cover is 62 percent, and on day 200, the vegetation cover is 79 percent. Based on productivity during each of these intervals, what was the average daily productivity rate (in terms of percent of cover) over the growing season? Please choose the correct answer from the following choices, and then select the submit answer button. 0.55 percent 1.23 percent 0.38 percent 0.12 percent 0.40 percent

0.38 percent

In a food web where each trophic level contains an ecological efficiency of 20 percent, what percent of the energy originally contained in producers is ultimately available to tertiary consumers? 20 percent 0.28 percent 0.8 percent 2.8 percent 0.2 percent

0.8 percent

A researcher wishes to calculate the biomass residence time of a zooplankton community in a lake. The researcher has determined that over 1 week, the biomass of... 10.3 g/m^3... 83 percent; a high assimilation efficiency, 55 percent.... 60 percent... 5.5 g/m^3, what is the biomass residence time for zooplankton? 0.9 weeks 2.39 weeks 0.51 weeks 10.3 weeks 1.95 weeks

1.95 weeks

You are working for the U.S. Department of Agriculture to measure energy transfer per corn plant in a cornfield. Each corn plant is exposed to 1,250 J of energy as sunlight. The consumption efficiency of this corn species is 2 percent, and the assimilation efficiency is 95 percent. If each corn plant respires 62 percent of assimilated energy, how much energy does each corn plant contain? 23.75 J 11.40 J 14.73 J 36.72 J 7.46 J

11.40 J

In a productive tropical forest, photosynthesis by plants captures 5,000 joules (J) of energy per square meter per year. However, approximately 60 percent of this energy is lost during plant respiration. What is the net primary productivity of this tropical forest? 3,000 J 3,500 J 2,000 J 1,500 J 1,000 J

2,000 J

How might you determine whether low precipitation or a low level of nutrients limits net primary productivity in a desert scrub ecosystem? Add water to some sites, add nutrients to other sites, add water and nutrients to other sites, and then determine where net primary productivity increases most. Decrease water in some sites, decrease nutrients in other sites, and then determine where net primary productivity decreases most. Add water to some sites, add nutrients to other sites, and then determine where net primary productivity increases most. Measure precipitation and nutrient levels to determine which is lower. Add water and nutrients to some sites, and then determine whether net primary productivity increases.

Add water to some sites, add nutrients to other sites, add water and nutrients to other sites, and then determine where net primary productivity increases most.

A team of scientists tests an innovative plan to remove excess CO2 from the atmosphere. In a pilot experiment, they attempt to increase primary productivity by adding nitrogen and phosphorus to coastal marine regions. They predict that the increased primary productivity will decrease dissolved CO2 levels in the ocean and cause CO2 from the atmosphere to dissolve into the water to maintain equilibrium. After 6 months, they find that net primary productivity has increased dramatically and CO2 levels at the study site are decreasing. The experiment continues, and 2 years later the team finds that CO2 levels in the ocean are increasing. As a result, the ocean is serving as a net source of CO2 to the atmosphere. How can you explain the change? Net primary productivity was actually silicon limited, so although the nutrients caused some increase in net primary productivity, the increases were not sustainable over the long term. Most of the nutrients were consumed by herbivores, which increased herbivore biomass and respiration over time. The added nitrogen and phosphorus slowly reacted with carbon to form excess CO2 in the water column. After the nutrients were used, many of the producers died, and their decomposition caused an increase in CO2 levels in the water. Increased producer biomass increased producer respiration, which caused an increase in CO2levels in the water.

After the nutrients were used, many of the producers died, and their decomposition caused an increase in CO2 levels in the water.

____ efficiency is the percentage of producer energy or biomass that is consumed by herbivores Assimilation Consumption Ecological Net production

Consumption

Why do researchers who study primary productivity in aquatic ecosystems typically measure changes in dissolved O2 levels rather than dissolved CO2 levels? It is not possible to measure dissolved CO2 underwater. Dissolved CO2 levels are typically very high, which makes small changes difficult to observe. Underwater plants use dissolved O2 for photosynthesis instead of dissolved CO2. Dissolved O2 is a more precise measurement of respiration. Dissolved CO2 is rapidly converted to other compounds in many aquatic ecosystems.

Dissolved CO2 is rapidly converted to other compounds in many aquatic ecosystems.

True or false? Greater accumulations of energy in a particular trophic level are associated with shorter energy residence times in that trophic level. True False

False

True or false? Satellite images of ecosystems that show a pattern of high absorption of green light and high reflectance of blue and red light indicate ecosystems with high standing crops of producers. False True

False

True or false? We can estimate gross primary productivity (GPP) using the following equation: GPP = NPP - Respiration. False True

False

Why do very high levels of precipitation (greater than 3 m/year) generally decrease net primary productivity? Increased osmosis decreases cellular solute concentrations. Important nutrients leach out of the soil. Harmful bacteria and fungi prefer very wet environments. Frequent rain clouds keep temperatures low. Plants get swollen with water and burst.

Important nutrients leach out of the soil.

Why do very high levels of precipitation (greater than 3 m/year) generally decrease net primary productivity? Plants get swollen with water and burst. Important nutrients leach out of the soil. Increased osmosis decreases cellular solute concentrations. Frequent rain clouds keep temperatures low. Harmful bacteria and fungi prefer very wet environments.

Important nutrients leach out of the soil.

Which statement is false? In aquatic ecosystems, more biomass is contained in tertiary consumers than in producers. In terrestrial ecosystems, less biomass is contained in secondary consumers than in primary consumers. In terrestrial ecosystems, more biomass is contained in producers than in primary consumers. In terrestrial ecosystems, less energy is contained in secondary consumers than in producers. In aquatic ecosystems, more energy is contained in primary consumers than in producers.

In aquatic ecosystems, more energy is contained in primary consumers than in producers.

Why does low silicon limit phytoplankton net primary productivity in aquatic ecosystems? Many phytoplankton require silicon to form structural shells. Silicon makes phytoplankton unpalatable to herbivores. Silicon is needed for phytoplankton photosynthesis. Silicon is a key nutrient for phytoplankton cellular reproduction. Phytoplankton use silicon to form amino acids.

Many phytoplankton require silicon to form structural shells.

Which of the following equations is used for calculating net primary productivity (NPP)? NPP = 1 ÷ (GPP - Respiration) NPP = GPP × Respiration NPP = GPP - Respiration NPP = GPP ÷ Respiration NPP = GPP + Respiration

NPP = GPP - Respiration

You decide to perform a simple experiment to determine whether nitrogen or phosphorus is a more limiting nutrient in a pond in your backyard. Using a curtain that does not allow water, nutrients, or organisms to pass through, you divide your pond into four equal-sized quadrats (like a pie with four pieces). You randomly apply one of the following treatments to each quadrat: no nutrients (control), nitrogen only, phosphorus only, nitrogen and phosphorus. After 10 days, you measure net primary productivity (NPP) in each quadrat of your pond. You find the following results: Control NPP = 1.2 g C/m2/d; nitrogen only NPP = 1.3 g C/m2/d; phosphorus only NPP = 2.8 g C/m2/d; nitrogen and phosphorus added NPP = 2.8 g C/m2/d. Which is true about nutrient limitation in your pond? Neither nutrient is limiting. Nitrogen is the only limiting nutrient. Phosphorus is the only limiting nutrient. Nitrogen and phosphorus are both limiting nutrients.

Phosphorus is the only limiting nutrient.

Which equation is correct? NPP = GPP + respiration Respiration = GPP - NPP GPP = NPP - respiration NPP + GPP = respiration

Respiration = GPP - NPP

Which statement about assimilation efficiency is true? Assimilation efficiency typically decreases as trophic level increases. The highest trophic levels typically have the highest trophic efficiency. Assimilation efficiency is equal to consumption efficiency for many predators. Secondary consumers typically have lower assimilation efficiency than primary consumers. Assimilation efficiency is typically equal across trophic levels.

The highest trophic levels typically have the highest trophic efficiency.

The river continuum concept predicts changes in the biotic and abiotic environment as one moves through a watershed from small headwater streams (upstream) to large, fast-flowing rivers (downstream). Typically, aquatic net primary productivity increases as one moves from headwater streams to higher-order rivers. Given this, which would you NOT expect to be true as you move downstream? The total amount of nutrients will decrease. Light levels hitting the water surface will increase. Average water temperature will increase. Net secondary productivity will increase. Gross primary productivity will increase.

The total amount of nutrients will decrease. Light levels hitting the water surface will increase.

True or false? Humans assimilate more energy when they eat plants than when they eat meat. True False

True

Which of the following tells scientists that a specific environmental variable limits net primary productivity in an ecosystem? Seasonal changes in net primary productivity closely match changes in the variable. Plant tissues require high amounts of the variable to grow. When the variable is added, net primary productivity significantly increases. When the variable is reduced or eliminated, net primary productivity decreases. Low amounts of the variable of interest are present in the environment.

When the variable is added, net primary productivity significantly increases.

Net production efficiency is the percentage of _____. assimilated energy used for respiration consumed energy that is not assimilated available energy that is consumed and assimilated consumed energy used only for production of offspring assimilated energy used for growth and reproduction

assimilated energy used for growth and reproduction

The relationship between net primary productivity and net secondary productivity is generally positive, which suggests that _____. bottom-up control is an important driver of community structure higher herbivory rates cause higher primary productivity most standing producer biomass is eaten by secondary consumers producers and herbivores both assimilate energy with high efficiency higher producer biomass leads to higher secondary consumer biomass

bottom-up control is an important driver of community structure

If you add a source of carbon to an unproductive lake and observe a rapid increase in net primary productivity, you conclude that _____. there are no carbon inputs into the lake adding carbon and nitrogen would increase net primary productivity even more carbon is the most important nutrient for plant growth carbon is the limiting nutrient in that lake the lake is a net carbon sink

carbon is the limiting nutrient in that lake

To quantify the productivity of a large area of land via remote sensing from a satellite, measure the _____. amount of absorbance of green light change in absorbance of green light over time amount of reflectance of blue light and red light change in reflectance of green light over time change in reflectance of blue light and red light over time

change in reflectance of green light over time

Many aquatic zooplankton species grow spikes as a defense against being eaten by predators. What aspect of energy transfer would this affect? assimilation efficiency net production efficiency consumption efficiency biomass residence time

consumption efficiency

Which biome would have the highest number of trophic levels? desert tropical rainforest cultivated land grassland deep lake

deep lake

The study of the balance of nutrients in ecological interactions, such as between an herbivore and a plant, is known as _____. remote sensing ecological efficiency ecological stoichiometry physical geology biomass residence time

ecological stoichiometry

The primary purpose of ecological stoichiometry is for _____. calculating the statistical significance of ecological research studies revealing the limiting role of nutrients in specific ecosystems representing the amount of energy in a particular trophic group determining the percentage of consumed energy that is assimilated by an organism explaining why ecological efficiencies can vary between trophic levels

explaining why ecological efficiencies can vary between trophic levels

When estimating net primary productivity for perennial grasses by measuring only the aboveground biomass, we have to be cautious when making conclusions because _____. rates of respiration are not taken into account for perennial grasses extensive root systems of perennial grasses can have twice as much belowground biomass as aboveground biomass some perennial grasses obtain carbohydrates from mycorrhizal fungi and assimilate these carbohydrates into plant tissues results are skewed by the amount of water contained in perennial grass biomass there is no way to prevent or account for the amount of perennial grass biomass lost to herbivory

extensive root systems of perennial grasses can have twice as much belowground biomass as aboveground biomass

Most consumed biomass that is not assimilated by an organism is lost as _____. respiration reproduction feces heat energy regurgitation

feces

Which of following would you expect to have the highest net production efficiency? elephant frog rat hummingbird sloth

frog

High levels of which ecological factor can cause inaccuracies when primary productivity is measured using only plant aboveground biomass? CO2 light nutrients moisture herbivory

herbivory

Phytoplankton (floating algae) reach peak productivity in coastal waters throughout the world. Which feature of coastal waters is the most likely driver of this pattern? high average water temperatures high nutrient inputs relatively few consumers high annual precipitation rates low disturbance frequency

high nutrient inputs

In many aquatic ecosystems, unicellular floating algae are produced quickly and consumed at a very high rate by herbivores. Which of the following best describes the algal populations under these conditions? high productivity, high standing crop high productivity, low standing crop low productivity, high standing crop low productivity, low standing crop

high productivity, low standing crop

In many aquatic ecosystems, unicellular floating algae are produced quickly and consumed at a very high rate by herbivores. Which of the following best describes the algal populations under these conditions? high productivity, high standing crop low productivity, low standing crop low productivity, high standing crop high productivity, low standing crop

high productivity, low standing crop

Net primary productivity in terrestrial ecosystems tends to be higher in areas with _____. lower temperature and higher nutrient recycling rates lower precipitation and more sunlight higher temperature and lower nutrient recycling rates higher temperature and higher precipitation higher nutrient recycling rates and less sunlight

higher temperature and higher precipitation

In a light-dark bottle experiment, the gross primary productivity of algal cells in water is calculated by measuring the _____ over time in the light bottle _____ over time in the dark bottle. increase in CO2; minus the decrease in O2 increase in O2; minus the decrease in O2 decrease; in CO2; minus the increase in CO2 decrease in O2; plus the increase in O2 increase in O2; plus the decrease in O2

increase in O2; plus the decrease in O2

In terrestrial and aquatic ecosystems, respectively, when net primary productivity increases, terrestrial net secondary productivity _____ and aquatic net secondary productivity _____. decreases; increases increases; decreases decreases; decreases increases; increases

increases; increases

Which is known to limit phytoplankton productivity in the open ocean? manganese zinc lead iron copper

iron

Which would typically be of most concern to a crop farmer? respiration gross primary productivity belowground biomass net secondary productivity net primary productivity

net primary productivity

Which of the following is the correct way to calculate ecological efficiency? net production energy of a trophic level divided by assimilation energy of that trophic level net production energy of tropic level z minus net production energy of trophic level z plus 1 net production energy of tropic level z divided by net production energy of trophic level z minus 1

net production energy of tropic level z divided by net production energy of trophic level z minus 1

Which two nutrients have the strongest influence on net primary productivity in most aquatic and terrestrial ecosystems? zinc and nickel magnesium and silicon nitrogen and phosphorus sodium and carbon iron and potassium

nitrogen and phosphorus

In general, additions of _____ in both terrestrial and aquatic ecosystems tend to increase net primary productivity the most compared to controls. nitrogen plus phosphorus no nutrients phosphorus only carbon only nitrogen only

nitrogen plus phosphorus

You want to perform an experiment in a grassland plot to determine whether nitrogen or phosphorus is a more limiting nutrient. In your experimental control, you would add _____ to the soil. nitrogen and phosphorus only nitrogen a different resource, such as water, only phosphorus no nutrients

no nutrients

Most whales live in _____. the open ocean ....

the open ocean

What is the source of most energy that moves through ecosystems? carbon-based molecules heat nutrients chemosynthesis solar energy

solar energy

In which terrestrial biome is net primary productivity greatest? savanna grasslands boreal forests tropical rainforests temperate forests

tropical rainforests

In which terrestrial biome is net primary productivity greatest? savanna tropical rainforests boreal forests grasslands temperate forests

tropical rainforests

True or false? Approximately 99 percent of all solar energy that is available to producers either reflects off them or passes through their tissues without being absorbed. True False

true